It is common to drive a generator, compressor, pump or other process machine with a prime mover, such as an internal combustion engine. Most internal combustion engines have a speed, or range of speeds, at which they run most efficiently, which is normally measured in revolutions per minute. Also, most engines are designed and built to rotate in one direction only, typically counter-clockwise when facing the flywheel.
In many cases, the most efficient speed of the engine is different than the rotational speed required by the process machine. In other cases, it is not practical to run the engine at the speed required by the process machine. In such cases, it is beneficial to increase or decrease the speed of the engine with external gearing, rather than to adjust the running speed of the engine. It should also be noted that most process machines are designed and built to rotate in one direction only, very often in the same direction as the engine used as the prime mover (typically clockwise when facing the input shaft of the process machine).
External gearing that increases or decreases the speed of an engine's output shaft is referred to as a speed changer and is disposed between the engine and the process machine. Speed changers feature a high parts-count, which implies lower reliability and necessitates additional maintenance-related logistics. Speed changers are bulky, inefficient and cost-prohibitive. Therefore, there is a need for a more efficient speed changer that is also integrated with the engine, or prime mover, with a view to reducing the speed changer's size, complexity, and cost.
For example, if the lubrication and cooling system of the speed changer could be integrated with the engine lubrication system, speed changer components such as heat exchangers and associated plumbing could be eliminated to reduce the device's weight and complexity. Furthermore, integration of a speed changer with the engine reduces the additional activities and costs normally associated with speed changer maintenance to only those specified for normal engine maintenance.
There is also a need for a speed changer that uses gearing with increased efficiency. Moreover, a speed changer with a smaller envelope and weight is needed to reduce material costs and improve reliability. Lower manufacturing costs would provide possibilities for the use of speed changers in applications that would not otherwise be economically feasible.